Black outline around sun?

[Can Scanner]

I was shooting sunsets yesterday, and almost all of my shots have a thin black line around the sun. The wider shots look fine.
I've never seen this outline before. It almost looks like the EVF detail, but that's impossible. I was using Detail: 0, Coring: +7, and CineGamma V.
The sun is obviously blown out, but what is that outline doing there?

 

[DavidBeier]

Looks like an edge enhancment artifact. In general a detail setting of 0 is pretty mild as far as edge enhacnment goes but probably the difference between the cooler areas of the sun and the blown out portion was so extreme that it never the less ended up creating a line there. I've seen this on occasion with some deliberately overexposed shots I've done though I tend to have the detail higher. I'm guessing either opening your iris more so the whole sun blows out or closing it more so the backgound is in silloute but you get more subtle gradations in the sun will eliminate the problem.